General anaesthetic might be bad for children’s brains – but poverty, poor nutrition or delaying life-saving surgery is much worse, say experts.

An alarming new Australian study published this week linked a dose of ‘general’ anaesthetic with a small but significant dip in school performance and brain development for thousands of NSW schoolkids.

The findings, if confirmed, are concerning. But they shouldn’t change the way children are treated; childhood surgery is almost never optional, say experts.

What the study really does is add a serious note of urgency in the quest to understand how anaesthesia works – and to the search for a non-toxic alternative.

For the study, published in Pediatric Anesthesia this week, a team made up of researchers from the University of Sydney and several other research institutes looked at the school results for 211,978 children in NSW.

Of those, 37,880 had been exposed to general anaesthetic before they turned four. After correcting for other factors, like disadvantage, those children were revealed to have performed significantly worse at school than their peers.

Their odds of scoring below national standards for reading and writing increased by nearly a quarter, as did their odds of being considered ‘developmentally high-risk’.

“The size of the effect, it’s measurable, but it’s small when you compare it to big significant things – like nutrition, education or significant childhood illness,” says study co-author Dr Justin Skowno, from the University of Sydney.

“You have to look at tens to hundreds of thousands of children before you can see this small effect.”

That’s true, says The Alfred’s Professor Myles. But the finding is still concerning.

“The authors are being quite circumspect, which is a good thing. But if you speak to any parent and you tell them your child might have a 1 per cent reduction in their future intellectual capacity, it’s easy to say that’s irrelevant, but as a parent nobody would like to have any reduction of any sort.”

For years it’s been known exposure to large amounts of general anaesthetic does serious developmental damage to the brains of young animals. Around the world, researchers are frantically working to confirm if this is also the case for children.

‘General’ seems to affect young brains quite differently to those of adults.

Developing brains are very malleable, constantly growing new neurons. Theoretically, this makes them extremely sensitive to anything that interferes with consciousness.

“The young brain is a very, very busy place where these neurons are being bedded in if they are working properly, or trimmed away if they are not,” says Dr Skowno.

“If you interfere in any way with this very complex process, you could imagine a drug that generally slows that process down would affect development.”

But the study has issues, and should not be treated as the final word on the subject.

Trying to compare large populations of children while correcting for the many things that can affect their development – poverty, education, nutrition – is an inexact science.

“This study did try to correct, but you can only adjust for what you know about, and you can never adjust for things perfectly,” says Professor Andrew Davidson, head of anaesthesia research at the Murdoch Children’s Research Institute.

Professor Davidson, speaking on behalf of Australian and New Zealand College of Anaesthetists, pointed to a range of other studies that have shown no effect.

One major Australian study looking at general anaesthetic found no effect on two-year-olds – although it’s possible, says Professor Davidson, the effects take some time to manifest.

Should parents be concerned? No, say all three experts who spoke to Fairfax Media. The effect is small, and childhood surgery is almost never optional. But it does add urgency to the search for a non-toxic anaesthetic.